Magnetron assembly and method



Jan. 11, 1949.

P. 1.. SPENCER 2,458,802

MAGNETRON ASSEMBLY AND METHOD Filed March 50, 1942 5y (SQ/71AM,

wrney Pawn 'L @verwew Y Patented Jan. 11, 1949 MAGNETRON ASSEMBLY ANDMETHOD Percy L. Spencer, West Newton, Mass., assignor to RaytheonManufacturing Company, Newton, Mass., a corporation of DelawareApplication March 30, 1942, Serial No. 436,891

18 Claims. 1

This invention relates to a magnetron, and more particularly to amagnetron in which the (dimensions and configurations of the internalstructure determine the frequency of the oscillations generated.

Magnetrons of the foregoing type have heretofore been constructed bycarefully machining the casing or anode structure out of a solid blockof copper. Since the frequencies intended to be generated by suchmagnetrons are of wave lengths of the order of centimeters or evenfractions thereof, minute changes in the dimensions of any part of suchstructure would produce large changes in the frequencies generated.Therefore, in order to produce the proper frequency and also to keepvarious oscillating parts of the structure at the same naturalfrequency, the machining had to be carried out with extreme accuracy.This made the manufacture of such magnetrons slow and expensive.

An object of this invention is to devise a magnetron structure which canbe made rapidly and inexpensively without sacrificing the accuracy withwhich the component parts are made.

Another object is to devise a magnetron structure and a method of makingthe same which can be carried out on a mass production basis byrelatively unskilled operators.-

The foregoingand other objects of this invention will be best understoodfrom the following description of an exemplification thereof, referencebein had to the accompanying drawings,

wherein: I

Fig, 1 is a longitudinal cross-sectional View of a magnetron constructedin accordance with my invention; 7

Fig. 2 is a top view of one of the stamped laminas from which themagnetron casing is constructed;

Fig. 3 is a top view of another of the stampe laminas from which themagnetron casing is constructed;

Fig. 4 is a top view of one of the stamped end caps of the magnetron ofFig. 1; and

Fig. 5 is a view of an assembly jig illustrating the method ofassembling the laminas.

The magnetron illustrated in thedrawing com prises an envelope structureforming the anode of the magnetron, a cathode structure '2, and a pairof end caps 3 and 4. The anode structure is so arranged that when thedevice is placed between magnetic pole pieces 5 and 6, oscillations aregenerated, the frequency of which is determined by the geometry andinternal structure of the anode assembly. These oscillations are picked2 up by a coupling loop I, and are led to a suitable utilization device.

As pointed out above, heretofore the entire casing of the magnetron hadbeen made of carefully machined parts, thus rendering the manufacturevery slow and expensive. In accordance with my invention I construct thecasing of all stamped parts. Thus the anode structure is made up of aplurality of flat stamped laminas 8 and 9. Each lamina is formed with acentral opening I 0 and a plurality of radial slots, each terminating ina circular opening 12. The laminas 8 and 9 are intended to be stackedalternately. Each lamina 8 is of smaller outer diameter than that ofeach lamina 9, leaving projecting portions of the laminas 9 which fromcooling fins for the final form of the magnetron. In a practicalexample, each lamina 8 may be about two inches in diameter and eachlamina 9 may be bout three inches in diameter, while the thickness ofeach of them may be about .070 inch. These laminas are formed of somesuitable conducting material which may be readily and accuratelystamped. I'prefer to use copper.

The dies for stamping the laminas 8 and 9 may be made very accurately,and large numbers of such laminas can be stamped out of sheet copperwith such dies. The dimensions of the openings H] and I2 and of theslots H are critical in such a device. However, with the use of suchaccurate dies, these critical dimensions are readily obtained in thestamping of the laminas.

The end caps 3 and 4 likewise can be stamped from sheet copper. However,the dimensions of these caps are not as critical as those referred toabove. The caps 3 and 4 are each made with a central dish-shaped portionl3 surrounded by an annular rim M. The upper cap 3 is provided with twoconducting pipes l5 and I 6 which are hermetically sealed through thesides of the dishshaped portion l3. Sealed to the outer end of the pipeI5 is a glass seal I! through which a pair of cathode lead-in conductorsl8 and I9 extend. The cathode 2 comprises a sleeve 20 of a suitableconducting material such as nickel, and bearing a suitable emissivecoating on the external surface thereof. A desirable coating arrangementis that described and claimed in my copending application, Serial No.412,993, filed September 30, 1941, now Patent No. 2,411,601, datedNovember 26, 1946. A heater 2| is supported within the sleeve 29 byhaving its ends extend through insulating blocks 22 mounted in oppositeends of the sleeve 20. The ends of the heater 2| preferably carrytantalum shields 23 which tend to prevent electrons emitted from thecathode from passingv out through the ends of the central opening to thecaps 3 and 4. The lead-in. conductor !8 is connected to the upperextended end of the heater. The lead-in conductor I9 is connected to thesleeve 20 by a connector extending through an opening in the shield 23.The lower shield 23 may also be connected to the sleeve 20. By the abovearrangement, the lead-in conductors l8 and I9 may serve as the heatercurrent leads, the lead-in conductor 59 also serving as the cathodelead. The conductors l8 and I9 also serve to support the cathodestructure. In order to steady and center the cathode structure, a micaguide plate'24 is mounted Within the end cap 4. The guide plate 24 maybe supported in any convenient manner, as. by a plurality of supportingstuds 25 fastened to the cap 4. The guide plate 24 has a central openinginto which the lower extendedend of the heater 2 may be inserted duringassembly.

The conducting pipe preferably extends through thewall of the cap 3 andinto the interior of the magnetron structure. The outer end of the pipel6 carries a glass seal 26 through which is sealed a lead-in conductor21. The inner end of the conductor 2'! is" bent, passes through anopening in the sidewallof the tube 56, andis connected to one end of thecoupling loop 1. The other end of the coupling loop may be connected tothe. outer wall of the pipe l6. Loop 1 is in a plane at right angles tothe plane of Fig. 1', and thus is inductively coupled to one of thebores formed by the aligned openings l2 of the laminae 8 and 9. The pipe[6 may also have an additional conducting pipe 28? connected thereto.This conducting pi'pe surrounds the conductor 2-? and forms a concentrictransmissionline therewith so that the oscillations produced by thedevice may be transmitted to the desired point.

In order to form the anode structure, alternate Iaminas 9 and 8 maybeassembled in a stack on an assembly jig. 29', as shown, for example, inFig. 5. Preferably the end lamina'so'i such a stacl arethelargelaminas8'. The jig 29. maybeprovidedwith a central pin 30 corresponding to theopenings HI, and with a plurality of pins 3|" cor responding to theopenings l2. In this way, merely by stacking the l'arninas on the jig29,

thecorresponding openings in the laminas are aligned with each other;forming a'central bore in which the cathode is to be supported, and aplurality ofbores corresponding to the openings I2. Likewise the slots Hare aligned, formingradial passages interconnectingthe central bore withthe plurality of surroundingbores.

While assembling the laminas on the jig '29-, a. thin ring. of suitablesolder, such as silver, is inserted between each adjacent lamina. Thesesolder rings need only be placed at the outer edges of the laminae8,.extending from the outside perimeter thereof to a point: somewhatshort'of the outer edge ofthe openings l2. The'thickn'ess of each solderringmay be about .002 inch, for example. If desired, tin may be used asthe soldering metal.

After the: laminas? and. solder rings have been assembled on the jig 29;they are clamped together, and the assemblyis passed through a hydrogen'furnace. This causes the solder to melt, andifuses' thestack of laminasinto herm'etical ly-tight unitary block. is removed before the assemblyis placed in" the furnace; although it may be left in place until afterthe assembly. is removed from the furnace;

Preferably the. jig 29" through'the' hydrogen furnace.-

In the latter case the pins 30 and 3! may be oxidized or graphitized ontheir surfaces in order to prevent any solder sticking thereto.

The cap 3 is assembled with the pipes l5 and i6 carrying theirrespective seals and lead-in conductors. These pipes are preferablysoldered in place by means of silver solder. The cathode assembly maythen be mounted on the lead-in conductors I8 and i9, and the couplingloop 1 maybe mounted on the lead-in conductor 21 and the pipe Hi. Thecap 4 is assembled with the guide plate 24, and is then soldered inplace on the lower end of the anode block. The upper cap 3 is thenplaced in position, care being taken that the lower extended end of theheater 2! projects through the central opening in the guide plate 24.Thereupon the cap 3 may be soldered in place on the anode block. Themagnetron may then be evacuated and freed of occluded gases inaccordance with the usual practice, and the cathode may be properlyactivated, which completes the construction.

It will be seen that in the completed assembly the anode structure'isprovided with a plurality of wedge-shaped arms, the faces of which areadjacent the cathode and cooperate as anode sections with the cathode. Acapacity exists between the cathode 2- and each such anode face. Alsocapacitanc'e's exist between the side walls of each of the aligned slotsH. The inner walls of the aligned openings 12 constitute inductances.When" the magnetron is energized and placed'between the pole pieces 4and 5, it generates os'cillations as mentioned above; The frequency ofthese oscillations is determined by the inductances and c'apacitancesabove mentioned. These inductances and capacitanc'es constitute resonantcircuits at the desired frequency, and each of the resonant circuitscooperates with each other resonant circuit to contribute to and enhancethe oscillations produced by the tube as a whole.

A magnetron as constructed above is readily made sothat each of theresonant circuits has exactly the proper natural frequency Without theexpensive and time-consuming machining which heretofore had beennecessary. If increased accuracy is desired, the anode structure mightbe placed in a coin" or sizing die after it has been In this Way anyslight inaccuracy in size of parts is eliminated by pressing the metalof the anode block to the exact size as determined by the sizing die.All of the' operations required to produce a magnetron as described'above may be performed by relatively unskilled operators, and lendthemselves readily to mass' production methods. The time for makingm'a'gnetrons is greatly decreased over that which had heretofore beennecessary, and the cost thereof isgreatly decreased.

Of course it is to be understood that this invention is not limited tothe particular details as described above as many equivalents willsuggest themselves to those skilled in the art. It is accordinglydesired that the appended claims be given a broad interpretationcommensurate with the scopeof the invention within the art.

What is claimed is 1 1. An electron discharge device comprising a metalenvelope enclosing an elongated cathode and electrode elements betweenwhich a space discharg'e'is adapted to take place, said envelope beingformed integrally with said electrode elements, end caps on saidenvelope, one end of said cathode beingc'arried by one of said end caps,a projection on the other end of said cathode, and an insulating platecarried by the other of said end caps, said plate having an opening intowhich said projection of said cathode extends.

2. An electron discharge device comprising a metal envelope enclosingelectrode element-shetween which a space discharge is adapted to takeplace, said envelope being formed integrally with certain of saidelectrode elements forming an electrode structure having a configurationcon.- stituting capacitance and inductance. elements forming circuitswhich are adapted to have oscillations set up therein, and an end capfor said envelope, said end cap carrying a coupling loop held adjacentone of said inductance elements, one end of said loop being connected tosaid end cap, the other end of said loop being connected to a conductorinsulatingly sealed through said end cap.

3. A discharge tube comprising a cathode surrounded by a laminated anodeblock, said anode block consisting of a series of stacked laminas, eachlamina having a central cathode space, and a plurality of spacesinterconnected with said cathode space and forming coupled cavityresonators.

4. An electron discharge device comprising a cathode, a laminated anodeblock adjacent said cathode, said anode block comprising a series ofstacked laminas, each lamina having a cathode space, and a space forminga cavity resonator connected to said cathode space.

5. An electron discharge device comprising an envelope containing acathode surrounded by a laminated anode block, said anode blockcomprising a series of stacked laminas, each lamina having a centralcathode space, and a plurality of spaces interconnected with saidcathode space and forming coupled cavity resonators, said anode blockconstituting a wall member of said envelope, certain of said laminasbeing of increased diameter extending beyond other of said laminas andforming cooling fins.

6. The method of forming a laminated anode block of an electrondischarge device having a cathode space and a cavity resonator, saidmethod comprising forming a plurality of copper laminas, each having acathode space, and a space forming a cavity resonator, stacking saidlaminas into the anode configuration with an intervening lamina ofsilver solder between each lamina, placing said stacked laminas in anatmosphere comprising hydrogen, and raising said stacked laminas to atemperature at which said solder laminas fuse.

'7. The method of forming a laminated anode block of an electrondischarge device having a cathode space and a cavity resonator, saidmethod comprising forming a plurality of sheet metal laminas, eachhaving a cathode space, and a space forming a cavity resonator, stackingsaid laminas into the anode configuration with an intervening lamina ofsilver solder between each lamina upon a jib having aligning membersprojecting into said cathode space and said cavity resonator formaintaining said laminas in the desired configuration, said aligningmembers having surfaces which are nonadherent to said solder when saidsolder is fused, and raising said stacked laminas to a temperature atwhich said solder laminas fuse.

8. The method of forming a laminated anode block of an electrondischarge device having a cathode space and a cavity resonator, saidmethod comprising forming a plurality of copper laminas, each having acathode space, and a space forming a cavity resonator, stacking saidlaminas into the anode configuration with an intervening lamina ofsilver solder between each lamina upon a jig having aligning membersprojecting into said cathode space and said cavity resonator formaintaining said laminas in the desired configuration, said aligningmembers having surfaces which are non-adherent to said solder when saidsolder is fused, placing said stacked laminas'in in an atmospherecomprising hydrogen, and raising said stacked laminas to a temperatureat which said solder laminas fuse.

9. An electron discharge device comprising a tubular anode, a cathode inand coaxial with said anode, said anode comprising a plurality ofindividual discs of sheet metal with central holes corresponding in sizeand shape with the desired internal cross-sectional size and shape ofsaid anode, said discs being stacked with said holes in registry andbeing hermetically joined together, the inner edges of the discs beingexposed directly to said cathode.

10. An electron discharge device comprising a hollow anode electrode,the walls of said elec trode being laminated, the laminas extendingtransversely through the wall of the electrode to its outside surfacefrom its inside surface, and the laminas being hermetically sealedtogether.

11. An anode comprising a plurality of stacked metal discs, the discshaving registering irregular shaped openings within the peripheries ofthe discs, the size and shape of the holes corresponding to the desiredcross-sectional configuration of the inner wall of the anode, thecontacting faces of the discs being hermetically sealed together.

12. An anode comprising a laminated tubular member, the laminas of themember comprising metal discs with central openings stacked in parallelplanes transverse to the axis of the memher with the sides of the discsin contact and with some of the spaced discs in the stack extendingoutwardly beyond the outer wall of the member.

13. A laminated tubular anode, the laminas of the anode comprisingsilver-plated sheet copper discs with registering openings, the silversurfaces of the discs being hermetically sealed toether.

14. An electron discharge device comprising a tubular anode, a cathodeconcentric with and in the anode, said anode comprising a plurality ofmetal discs hermetically joined along their peripheries, each dischaving a central hole and a plurality of radially extending slots fromsaid hole, the discs being stacked with the slots of each of said discsbeing disposed one above the other to provide cavities, of the desiredlongitudinal configuration, about said cathode.

15. A laminated tubular anode, the laminas of the anode comprising aplurality of thin sheet metal discs, the discs each having a round holeand a communicating narrow slot, the holes and slots being in registryin the stack of discs to define a cylindrical bore and an elongatednarrow cavity extending longitudinally of the anode.

16. The method of fabricating a tubular envelope wall for an electrondischarge device, the wall having spaced cooling fins on its outsidesurface and having an electron collecting area of any desiredconfiguration on its inside surface, comprising cutting two groups ofmetal discs of differ ent diameters, cutting holes having the desiredconfiguration in the first group of metal discs, cutting holes havingsaid configuration in the sec- 0nd group of Inetaldiscs, stackingandinterleav-- ing thediscs of the two groups with their, holesinregistry, and hermetically joining, the. discs.

17. A fabricated tubular envelope wallfor an electron discharge devicecomprising a first group of metal discs having holes of thedesiredconfiguration in said discs, a second group of metal discs havingoutside diameters larger than the outside diameters of said first groupofmetal discs and having holes cut in the discs corresponding to theholes of said first group of metal discs, the discs of the two groupsbeing, stacked and interleaved, with the holes ofthe discs in registry,and the discs all being hermetically joined together.

18. A cathode mounting comprising a cathode, afilament within saidcathode with the ends of the-filament projecting at the ends of thecathode, a support opposite the end of the cathode, one end of saidfilament, being within and held by said support, and a conductive platebetween said support and cathode and secured to said last-named end.

PERCY L. SPENCER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,684,947 Daumann Sept. 18, 19281,787,082 McCullough Dec. 30, 1930 1,879,544 Scognamillo et a1. Sept.27, 1932 2,043,733 I Brasch et al June 9, 1936 2,063,342 Samuel Dec. 8,1936 2,121,598 Kerschbaum et a1. June 21, 1938 2,183,157 Samuel June 20,1939 2,186,127 Samuel Jan. 9, 1940 2,289,984 Mouromtseff et a1. July 14,1942 2,305,781 Helbig Dec. 22, 1942 FOREIGN PATENTS Number Country Date216,562 Great Britain May 23, 1924 509,102 Great Britain July 11, 1939

